One purpose of this study is to show theoretically the potential of a monocycle technique to detect and identify salt water wedges under dissipative fresh water. Also, the potential use for bathymetry is discussed, in particular for bodies of water of extremely low salinities as may be expected in some parts of the Baltic Sea, in Fjords and in large estuaries. The importance of bathymetry for military operations in shallow water is well known. It happens to be that some bodies of water with very low salinity are in areas of particular military sensitivity. Salt water wedges are of military importance for small submarines, swimmers and swimmer delivery vehicles and mine and counter mine warfare.